{"id":2227576,"url":"http://patchwork.ozlabs.org/api/1.1/covers/2227576/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/cover/20260424-master-v2-0-8b50b5c063ed@gmail.com/","project":{"id":14,"url":"http://patchwork.ozlabs.org/api/1.1/projects/14/?format=json","name":"QEMU Development","link_name":"qemu-devel","list_id":"qemu-devel.nongnu.org","list_email":"qemu-devel@nongnu.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20260424-master-v2-0-8b50b5c063ed@gmail.com>","date":"2026-04-23T21:36:37","name":"[v2,0/3] linux-user: Filter /proc/*/task/ and validate tkill targets","submitter":{"id":93154,"url":"http://patchwork.ozlabs.org/api/1.1/people/93154/?format=json","name":"Ali Raza","email":"elirazamumtaz@gmail.com"},"mbox":"http://patchwork.ozlabs.org/project/qemu-devel/cover/20260424-master-v2-0-8b50b5c063ed@gmail.com/mbox/","series":[{"id":501265,"url":"http://patchwork.ozlabs.org/api/1.1/series/501265/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/list/?series=501265","date":"2026-04-23T21:36:37","name":"linux-user: Filter /proc/*/task/ and validate tkill targets","version":2,"mbox":"http://patchwork.ozlabs.org/series/501265/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/covers/2227576/comments/","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=AIdOphpZ;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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charset=\"utf-8\"","Content-Transfer-Encoding":"8bit","X-B4-Tracking":"v=1; b=H4sIAOWQ6mkC/2WNwQ7CIBAFf6XZsxhAa4wn/8P0QGFp10gxgETT8\n O9CPXqcZN68FSIGwgiXboWAmSL5pYLcdaBntUzIyFQGyeWJH0XPnIoJAzsobpXE0UrTQ5WfAS2\n 9t9Bt+HF8jXfUqa2bMVNMPny2pyya9xfNgnF2NkaiFUIg4nVyih577R0MpZQv+dJ/Wq4AAAA=","X-Change-ID":"20260415-master-3a0fa2ebf2d5","To":"qemu-devel@nongnu.org","Cc":"Ali Raza , Laurent Vivier ,\n Pierrick Bouvier ,\n =?utf-8?q?Alex_Benn=C3=A9e?= , deller@gmx.de","X-Mailer":"b4 0.15.2","Received-SPF":"pass client-ip=2a00:1450:4864:20::42a;\n envelope-from=elirazamumtaz@gmail.com; helo=mail-wr1-x42a.google.com","X-Spam_score_int":"-20","X-Spam_score":"-2.1","X-Spam_bar":"--","X-Spam_report":"(-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1,\n DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001,\n RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001,\n SPF_PASS=-0.001 autolearn=ham autolearn_force=no","X-Spam_action":"no action","X-Mailman-Approved-At":"Thu, 23 Apr 2026 20:42:33 -0400","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"qemu development ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"},"content":"This series fixes a problem where QEMU user-mode exposes internal\nhost threads (RCU, TCG workers) to guest processes via /proc/*/task/\nand allows the guest to signal them via tkill/tgkill.\n\nPatch 1: Filters getdents/getdents64 on /proc//task/\nPatch 2: Validates tkill/tgkill targets against guest CPU list\nPatch 3: Adds a multiarch test exercising both fixes\n\nSigned-off-by: Ali Raza \n---\nChanges in v2:\n- linux-user/syscall.c: use pid_t instead of long for the tid variable\n in do_getdents() and do_getdents64() (suggested by Helge Deller).\n- linux-user/syscall.c: replace ad-hoc readlink-at-getdents check with\n fd_trans-based tagging at open time, eliminating a TOCTOU race and\n a broad-prefix match that also matched /proc//task//fd.\n- linux-user/syscall.c (do_getdents, do_getdents64): retry sys_getdents\n when an entire host batch is filtered out, so the guest does not see\n a false EOF.\n- linux-user/syscall.c (do_getdents, do_getdents64): parse the dirent\n TID with qemu_strtoi() instead of strtol() so out-of-range values\n cannot wrap silently into pid_t.\n- linux-user/syscall.c (do_tkill): validate the guest tid range against\n pid_t and only reject signals whose target lives in our own host\n process and is not a guest thread (allow cross-process tkill to fall\n through to the kernel).\n- linux-user/syscall.c (do_tgkill): drop the previous tgid==getpid()\n blanket rejection and apply the same in-our-process-only filter, so\n legitimate cross-process tgkill keeps working.\n- tests/tcg/multiarch/linux-proc-task.c: hard-assert ESRCH on tkill to\n a non-guest tid, and add tgkill coverage (success on guest tids,\n ESRCH on a wrong tgid).\n- Link to v1: https://lore.kernel.org/qemu-devel/20260415-master-v1-0-8dd2ef111eee@gmail.com\n\nTo: qemu-devel@nongnu.org\nCc: Laurent Vivier \nCc: Pierrick Bouvier \nCc: Alex Bennée \n\n---\nAli Raza (3):\n linux-user: Filter /proc/*/task/ to hide QEMU-internal threads\n linux-user: Validate tkill/tgkill targets are guest threads\n tests/tcg: Add test for /proc/self/task/ filtering and tkill validation\n\n linux-user/fd-trans.c | 6 +\n linux-user/fd-trans.h | 18 ++\n linux-user/syscall.c | 353 +++++++++++++++++++++-------\n tests/tcg/multiarch/Makefile.target | 2 +\n tests/tcg/multiarch/linux/linux-proc-task.c | 193 +++++++++++++++\n 5 files changed, 492 insertions(+), 80 deletions(-)\n---\nbase-commit: da6c4fe60fee30dd77267764d55b38af9cb89d4b\nchange-id: 20260415-master-3a0fa2ebf2d5\n\nBest regards,\n-- \nAli Raza "}